The present invention relates to improved methods and compositions for drilling boreholes such as oil wells, gas wells or the like.
Drilling fluids used in the drilling of oil wells, gas wells and similar boreholes are commonly aqueous mixtures containing clays or other collodial materials as well as certain other additives which are employed depending on borehole conditions. The drilling fluid serves as a lubricant for the bit and drill stem, as a carrying medium for the cuttings produced by the drill bit, and assists in the formation of a filter cake on the walls of the borehole to minimize fluid losses to the surrounding subsurface strata through which the borehole extends. In most cases, the viscosity of the drilling fluid must be high enough to effectively remove the cuttings from the borehole. On the other hand, excessive viscosities are undesirable because excessive pump pressure is necessary to circulate such high viscosity drilling fluid. Moreover, such excessive pressures in the borehole increase the likelihood of fractures in the subsurface strata leading to a loss of whole drilling fluid to the formation.
The prior art abounds with numerous drilling fluid compositions designed to provide the proper viscosity for the particular borehole drilling application. Generally, in order to achieve and maintain the desired viscosity, the prior art drilling fluids have complex compositions and/or require complex, time consuming formulation procedures in their preparation. Additionally, due to the complex make-up of the drilling fluid and/or the mixing procedures, skilled personnel are required for their preparation. It will be appreciated that there are numerous instances where the ability to rapidly prepare the drilling fluid at the drilling site is not only desirable but expedient. Further, the ability to easily and quickly effect, on-site, large viscosity changes in the drilling fluid can be extremely useful.